Various attempts have been made to produce peptides by transforming animal cells and culturing the transformants. Examples thereof are listed below together with the approximately calculated productivities.
(i) BPV (bovine papilloma virus)-mouse C127 system: Human IFN-.gamma. gene (cDNA), SV40 early promoter; 3.times.10.sup.5 u/ml (R. Fukunaga et al., Proc. Natl. Acad. Sci. USA, 81, 5086 (1984)); PA1 (ii) SV40-CV-1 system: Human IFN-.beta. gene (cDNA), SV40 early promoter; 2.times.10.sup.4 u/ml (D. Gheysen et al., J. Mol. Appl. Genetics, 1, 305 (1982)); PA1 (iii) SV40-COS system: Human insulin gene (cDNA), SV40 early promoter (O. Laud et al., J. Biol. Chem., 258, 6043 (1983)); PA1 (iv) Eco-gpt-CHO system: Human IFN-.gamma. gene (cDNA), SV40 early promoter; 1.times.10.sup.4 u/ml (T. Kadotani et al., Seikagaku, 56, 915 (1984)); and PA1 (v) dhfr-CHO system: Human IFN-.gamma. gene (cDNA), SV40 early promoter; 1.times.10.sup.5 u/ml (S. Scahill et al., Proc. Natl. Acad. Sci. USA, 80, 4654 (1983)).
Although each of these methods has its characteristic features, each method is still unsatisfactory, in particular in the productivity of the desired peptide.
Myelomas have also been used as antibody-producing cells in the production of monoclonal antibody peptides However, their use in the production of other peptides has not yet been known.